To establish a range of radiation doses for pediatric gated cardiac CT angiography (CTA).

The following gated cardiac CT (GE LightSpeed 16-slice Snap shot burst plus) was preformed on a 5 year-old anthropomorphic phantom (CIRS, Norfolk, VA): diagnostic phase - carina to apex, retrospective gating (100 bpm HR simulator) with multiphase recon, 16 x 0.625, .5 sec, .275 pitch, 120 kVp (at 120, 220, and 330 mA), 80 kVp (385 mA which is estimate of comparable noise to 120 kVp/220 mA protocol) and additional timing bolus phase was performed at 32 mAs, 4-slice, 120 kVp. Organ doses were measured using MOSFET technology (3 runs for each protocol, averaged). CTDIvol and DLP were also recorded from which effective dose (ED) was calculated (ICRP 60 guidelines).

Organ dose measurements included breast, ranging from 3.5 cGy to 12.6 cGy and bone marrow, ranging from 1.7 cGy to 7.6 cGy between low and high mA CT. 80 kVp/385 mA produced less radiation dose to all organs than the 120 kVp/220 mA exam. Diagnostic phase CTDIvol and DLP ranged up to 68.89 mGy and 676.03 mGy.cm respectively (large FOV) for highest mA scan. ED (mSv) were as follows: 110 mA: 7.4 +/- 0.6; 220 mA: 17.2 +/- 0.3; 330 mA: 25.7 +/- 0.3; 80 kVp/385 mA: 10.6 +/- 0.2. Timing bolus phase EDE was 2.7 +/- 0.1.

Radiation doses to children during gated cardiac CTA varies greatly depending on parameters, but may be extremely high with ED reaching 28.4 mSv (combined diagnostic and timing bolus phases). It is likely that the ED to children is actually higher given limitations of ICRP 60 estimations in children. Breast dose can be particularly high. Further work with determination of lower mA and image quality is extremely important before routine use of gated cardiac CTA in children.

D.P.F.: Medical Advisor GE
Research Support GE